1. Field of the Invention
The present invention relates to an endoscope apparatus that displays on the same screen a front observation image taken in from a front-viewing observation window in a distal end surface at a distal end portion of an inserting section and a side observation image taken in from a side-viewing observation window on a periphery of a side surface of the distal end portion.
2. Description of the Related Art
In a generally used endoscope apparatus, a front-viewing observation window through which an inserting direction (an axial direction) is imaged in a predetermined viewing region, an illumination window through which illumination light for observation is applied, a forceps hole through which a forceps or the like is extended, and others are arranged on a distal end surface of an inserting section. An imaging lens group (an imaging optical system) and an imaging element are arranged behind this front-viewing observation window, and the imaging element photo-electrically converts an observation light image formed by the imaging lens group to generate a video signal and displays it as a front observation image on, e.g., a monitor.
Further, for example, in Japanese Patent No. 4955838 is suggested an endoscope apparatus having a side-viewing observation window formed of a cylindrical optical element that takes in a side observation target on a lateral periphery orthogonal to the axial direction (the inserting direction) mounted therein in addition to a front-viewing observation window. For example, observation using a colonoscope apparatus involves the possibility that oversight might occur unless observation is carefully performed while rotating a bending section since the colon as an observation target has many rugae. Thus, mounting the side-viewing observation window expands an angle of a viewing field region, thereby further avoiding the oversight.
The front-viewing observation window and the side-viewing observation window are observation windows provided in one optical lens, and observation light images taken in from the respective observation windows are simultaneously formed by using the same optical system and sectioned and projected onto the same light receiving surface of the imaging element. Thus, a front observation image taken in from the front-viewing observation window and a side observation image taken in from the side-viewing observation window are sectioned and enter the same light receiving surface, and a combined observation image is generated by photoelectrical conversion and displayed on a monitor.
In the same monitor display screen, since a screen of a combined image of a front observation image and a side observation image has a smaller display region (a screen size) of the front observation image than a regular screen (the front observation image alone), observation properties are deteriorated with respect to an operator. Further, an operator or a manipulator may experience a strange sensation of perspective or depth, thus requiring reviewing the image.
It is, therefore, an object of the present invention to provide an endoscope apparatus that provides a sufficient display region for a front observation image even in case of a combined image formed of the front observation image and a side observation image and reduces a sensation of strangeness etc., without deteriorating observation properties.